Fuel pump

ABSTRACT

A fuel pump includes a pump cover on one side of a housing, a cover end portion on the other side of the housing, a stator inside the housing, a rotor inside the stator, a shaft rotatable with the rotor, an impeller rotatable with the shaft to pressurize fuel inside the housing, a bearing portion provided in the cover end portion on its center axis to slidably support an end part of the shaft, and a relief valve capable of reducing a fuel pressure inside the housing. The cover end portion has an end surface located on its side opposite from the pump cover, and the relief valve includes a valve seat located on an opposite side of the end surface of the cover end portion from the pump cover.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by referenceJapanese Patent Application No. 2012-127810 filed on Jun. 5, 2012.

TECHNICAL FIELD

The present disclosure relates to a fuel pump which supplies fuel to afuel-supplied object.

BACKGROUND

Conventionally, a fuel pump is known which draws a fuel through asuction portion and discharges the drawn fuel through a dischargeportion by rotating an impeller with use of an inner-rotor motor (see,for example, Patent Document 1: JP 2012-31807 A). Discharge performanceof the fuel pump, such as an amount and a pressure of fuel dischargedfrom the discharge portion, depend on rotation of the motor. Thus, it isnecessary to keep accuracy high in processing of an inner wall of abearing portion that supports a shaft of the motor.

A fuel pump of Patent Document 1 includes a relief valve. The reliefvalve is capable of reducing a fuel pressure in a space provided betweena pump cover and a cover end in a housing by separating a valve memberfrom a valve seat when the fuel pressure becomes higher than or equal toa predetermined value. Accordingly, it is limited that, for example, thefuel pump or a supply pipe conveying fuel to a fuel-supplied object isdamaged due to excess pressure increase in the housing. In this case,the cover end has an end surface on its side opposite from the pumpcover, and the valve seat of the relief valve is located in the coverend, i.e., on a near side of the end surface of the cover end to thepump cover. In other words, the valve seat is located at a position nearto a bearing portion that slidably supports a shaft. When the valve seatis formed by, for example, heat forming or cutting in a manufacturingprocess of the fuel pump, an inner wall of the bearing portion may bedeformed due to the forming of the valve seat. Additionally, in the fuelpump of Patent Document 1, a press-fit part is provided in an outer rimof the cover end that has a circular plate shape, and the press-fit partis press-fitted to an inner side of an end part of the housing. Thepress-fit part may also be deformed due to the forming of the valveseat. When the inner wall of the bearing portion or the press-fit partis deformed, support of the shaft by the bearing portion may becomeunstable in use of the fuel pump. Therefore, rotation of the shaft andan impeller may be destabilized, and a fuel discharge capacity of thefuel pump may become unstable.

SUMMARY

It is an objective of the present disclosure to provide a fuel pumpcapable of limiting deformation of a component due to forming of a valveseat of a relief valve.

According to an aspect of the present disclosure, a fuel pump includes ahousing, a pump cover, a cover end portion, a stator, a rotor, a shaft,an impeller, a bearing portion, a discharge portion and a relief valve.The housing has a hollow cylindrical shape, and the pump cover closes anend opening of the housing on a first side of the housing in an axialdirection of the housing. The pump cover includes a suction portion. Thecover end portion has a circular plate shape to close the other endopening of the housing on a second side of the housing in the axialdirection of the housing, and the cover end portion includes a press-fitpart that is located on an outer rim of the cover end portion to bepress-fitted to an inner side of the housing. The stator has a hollowcylindrical shape, and the stator is accommodated inside the housing andincludes a plurality of wound wires. The rotor is rotatably providedinside the stator, and the shaft is provided coaxially with the rotor torotate together with the rotor. The impeller is connected to one end ofthe shaft, and the impeller rotates together with the shaft to draw afuel through the suction portion and pressurize the drawn fuel. Thebearing portion is provided in the cover end portion on a center axis ofthe cover end portion to slidably support the other end of the shaft.The discharge portion is provided in the cover end portion to be used asa port through which the fuel pressurized by the impeller is discharged.The relief valve is capable of reducing a fuel pressure in a space thatis located between the pump cover and the cover end portion inside thehousing when the fuel pressure in the space becomes higher than or equalto a predetermined value. The relief valve includes a cylindricalportion, a valve seat, a valve member and an urging member. Thecylindrical portion is integrated with the cover end portion to protrudeoutward from an end surface of the cover end portion on the second sideof the housing. The valve seat is provided inside the cylindricalportion, and the valve member is capable of contacting the valve seat.The urging member has an end part contacting the valve member to urgethe valve member toward the valve seat. The valve member is separatedfrom the valve seat when the relief valve reduces the fuel pressure inthe space, and the valve seat is located outside the cover end portionon the second side of the housing.

Accordingly, the end surface of the cover end portion is located on aside of the cover end portion opposite from the pump cover, and thevalve seat is located on an opposite side of the end surface of thecover end portion from the pump cover. In other words, the valve seat islocated on an opposite side of the cover end portion from the bearingportion and outside the cover end portion. Hence, although the valveseat is formed by, for example, thermal forming or cutting in amanufacturing process of the fuel pump, deformation of an inner wall ofthe bearing portion or the press-fit part due to the forming of thevalve seat can be restricted. Therefore, rotation of the shaft and theimpeller can be stabilized, and fuel discharge performance of the fuelpump can be made to be stable.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with additional objectives, features andadvantages thereof, will be best understood from the followingdescription, the appended claims and the accompanying drawings, inwhich:

FIG. 1 is a partially sectional view, taken along a line I-I in FIG. 2,showing a fuel pump according to an exemplar embodiment of the presentdisclosure;

FIG. 2 is a sectional view taken along a line II-II in FIG. 1;

FIG. 3 is a view showing the fuel pump viewed in a direction of an arrowIII in FIG. 1; and

FIG. 4 is a schematic diagram showing a cutting process of a cover endportion of the fuel pump according to the exemplar embodiment.

DETAILED DESCRIPTION

An exemplar embodiment of the present disclosure will be describedhereinafter referring to FIGS. 1 to 3. A fuel pump 1 draws a fuel from afuel tank to discharge and supply the fuel to an internal combustionengine that is a fuel-supplied object to which a fuel is supplied. Asshown in FIGS. 1 and 2, the fuel pump 1 includes a housing 10, a pumpcover 20, a cover end portion 30, a stator 40, a rotor 50, a shaft 52,an impeller 55, a discharge portion 36 and a relief valve 90.

The housing 10 is made of metal such as iron to have a cylindricalhollow shape. An outer periphery of the housing 10 is coated with zincor tin, for example. The pump cover 20 is made of metal such as aluminumto have an approximately circular plate shape, and is located on one endof the housing 10 in an axial direction of the housing 10 to close anopening of the housing 10. The pump cover 20 is fixed to an inside ofthe one end of the housing 10 by crimping the one end of the housing 10radially inward, so that the pump cover 20 is prevented from beingdetached from the housing 10 in the axial direction. As shown in FIG. 1,the pump cover 20 includes a suction portion 21 having a cylindricalshape. The suction portion 21 has a suction passage 211 that extendsthrough the pump cover 20 in a plate thickness direction of the pumpcover 20.

The cover end portion 30 is made, for example, of resin to have acircular plate shape. The cover end portion 30 is located on the otherend of the housing 10 in the axial direction of the housing 10 to closeanother opening of the housing 10. The cover end portion 30 includes apress-fit part 31 on an outer rim of the cover end portion 30, and thepress-fit part 31 is press-fitted to an inside of the other end of thehousing 10. The cover end portion 30 is fixed to the inside of the otherend of the housing 10 by crimping the other end of the housing 10radially inward, so that the cover end portion 30 is prevented frombeing detached from the housing 10 in the axial direction.

The stator 40 includes sets of a core 41, an insulator 42 and a windingwire 43. The core 41 is made of a laminated core in which magnetic thinplates are laminated. The insulator 42 has a hollow cylindrical shape,and is fitted to an outer circumference of the core 41. The winding wire43 is wound around the insulator 42. The sets of the core 41, theinsulator 42 and the winding wire 43 are arranged in a circumferentialdirection of the housing 10 on an inner side of the housing 10. In thepresent embodiment, six sets of the core 41, the insulator 42 and thewinding wire 43 are arranged in the circumferential direction of thehousing 10 at predetermined intervals. The stator 40 and the rotor 50are used as a three-phase (U-V-W phase) brushless motor. Two windingwires 43 configure one phase such that three phases of winding wires 43are provided, and the three phases correspond to a U phase, a V phaseand a W phase of the three-phase brushless motor respectively.

As shown in FIGS. 1 and 2, the core 41, the insulator 42 and the windingwire 43 of the stator 40 are connected to each other by molding of resinthat is used as a material of the cover end portion 30. The stator 40 isintegrated with the cover end portion 30 by resin molding. The stator 40is formed in an approximately hollow cylindrical shape by the resinmolding of the core 41, the insulator 42 and the winding wire 43. Thestator 40 is accommodated in the housing 10 coaxially with the housing10. The core 41 is covered by the resin or the insulator 42 except for asurface of the core 41 opposed to a center axis of the stator 40.

The rotor 50 is made of, for example, a magnetic material such as a bondmagnet to have a cylindrical shape. The rotor 50 is provided on aradially inner side of the stator 40. The rotor 50 is magnetized suchthat north poles and south poles are arranged alternately in acircumferential direction of the rotor 50. The rotor 50 has a shaft hole51 provided on a center axis of the rotor 50. The shaft 52 is made ofmetal to have a pole shape, and is press-fitted to the shaft hole 51.The shaft 52 is rotatable together with the rotor 50.

A pump casing 60 is provided between the pump cover 20 and the stator40. The pump casing 60 is made of, for example, metal such as aluminumto have an approximately circular plate shape. The pump casing 60 has ahole portion 61 in a center part of the pump casing 60, and the holeportion 61 extends through the pump casing 60 in a plate thicknessdirection of the pump casing 60. A bearing member 62 is fitted into thehole portion 61 of the pump casing 60. The bearing member 62 is made of,for example, a copper-based sintered metal to have a hollow cylindricalshape.

The cover end portion 30 has a recess part 32 located on a near side ofthe cover end portion 30 to the rotor 50, and the recess part 32 of thecover end portion 30 concaves toward an opposite side of the cover endportion 30 from the rotor 50. The recess part 32 is located at a centerpart of a surface of the cover end portion 30 opposed to the rotor 50.The cover end portion 30 further includes a shaft cylindrical part 33that is provided at a center of the recess part 32 to protrudecylindrically toward the rotor 50. A center axis of the shaftcylindrical part 33 is coincident with a center axis Ax1 of the coverend portion 30. A bearing member 34 is fitted into an inner side of theshaft cylindrical part 33. Similar to the bearing member 62, the bearingmember 34 is made of, for example, a copper-based sintered metal to havea cylindrical shape.

The hole portion 61 supports one end side of the shaft 52 via thebearing member 62, and the shaft cylindrical part 33 supports the otherend side of the shaft 52 via the bearing member 34. Accordingly, therotor 50 and the shaft 52 are supported rotatably by the pump casing 60and the cover end portion 30 via the bearing member 62, the hole portion61, the bearing member 34 and the shaft cylindrical part 33. The shaftcylindrical part 33 of the cover end portion 30 may be used as anexample of a bearing portion that supports the other end of the shaft52.

The impeller 55 is made of resin to have an approximately circular plateshape. The impeller 55 is accommodated in a pump chamber 63 providedbetween the pump cover 20 and the pump casing 60. The pump chamber 63has an approximately circular plate shape. One end of the shaft 52 islocated in the pump chamber 63, and is chamfered to have a flat surfaceon its side wall. The impeller 55 has a hole 56 having a shapecorresponding to a shape of the chamfered one end of the shaft 52. Thehole 56 is located at a center part of the impeller 55. The one end ofthe shaft 52 is fitted into the hole 56 of the impeller 55. Therefore,the impeller 55 rotates in the pump chamber 63 when the shaft 52rotates.

The pump cover 20 has a groove 22 on its surface located on a near sideof the pump cover 20 to the impeller 55. The groove 22 has anapproximately C-shape when the groove 22 is viewed in the center axisAx1. The groove 22 communicates with the suction passage 211. The pumpcasing 60 has a groove 64 on its surface located on a near side of thepump casing 60 to the impeller 55. The groove 64 has an approximatelyC-shape when the groove 64 is viewed in the center axis Ax1. The pumpcasing 60 further has a through passage 65 that extends through the pumpcasing 60 in a plate thickness direction of the pump casing 60 tocommunicate with the groove 64 as shown in FIG. 1. The impeller 57includes a blade portion 57 at a position corresponding to positions ofthe grooves 22 and 64.

The discharge portion 36 is made of resin to be integrated with thecover end portion 30, and protrudes cylindrically from an end surface 35of the cover end portion 30. The end surface 35 of the cover end portion30 is located on an opposite side of the cover end portion 30 from thepump cover 20. In the present embodiment, the discharge portion 36 islocated at a position distant from the center axis Ax1 of the cover endportion 30 by a predetermined distance. The discharge portion 36 has adischarge passage 37 therein, and the discharge passage 37 communicateswith a space 11 that is provided inside the housing 10 between the pumpcover 20 and the cover end portion 30.

As shown in FIG. 1, the discharge portion 36 is connected to one end ofa supply pipe 2. The other end of the supply pipe 2 is connected to thefuel-supplied object (internal combustion engine). Accordingly, a fuelpressurized in the space 11 due to rotation of the impeller 55 isdischarged from the discharge portion 36 through the discharge passage37 to be supplied to the fuel-supplied object via the supply pipe 2. Inthe present embodiment, multiple terminals 44 are provided in the coverend portion 30, and the terminals 44 are made of metal to have a longplaty shape. Ends of the terminals 44 on one side in its longitudinaldirection are electrically connected to the winding wires 43, and endsof the terminals 44 on the other side in its longitudinal directionprotrude from the end surface 35 of the cover end portion 30 to beexposed to an outside of the fuel pump 1. In the present embodiment, thenumber of the terminals 44 is three, and the ends of the three terminals44 on the one side are electrically connected respectively to theU-phase, the V-phase and the W-phase of the winding wires 43. As shownin FIG. 3, the terminals 44 are arranged adjacent to the outer rim ofthe end cover portion 30 at intervals of approximately 60 degrees inangle in a circumferential direction of the cover end portion 30.

The ends of the terminals 44 on the other side in its longitudinaldirection are to be connected to a wire harness. When an electric poweris supplied to the winding wire 43 via the wire harness, a rotatingmagnetic field is produced in the stator 40. Accordingly, the rotor 50rotates, and the impeller 55 thereby rotates together with the shaft 52.As a result, fuel inside the fuel tank is drawn into the space 11through the suction portion 21 to be pressurized by the impeller 55,thereby being discharged from the discharge portion 36.

In the present embodiment, the fuel pump 1 further includes terminalsupport portions 71, 72 and 73 which are made of resin to be integratedwith the cover end portion 30. The terminal support portions 71, 72 and73 protrude from the end surface 35 that is located on the opposite sideof the cover end portion 30 from the pump cover 20. The terminal supportportions 71, 72 and 73 supports the three terminals 44 respectively, asshown in FIG. 3. In the present embodiment, the terminal supportportions 71, 72 and 73 are arranged in vicinity to an outer rim of theend surface 35 of the cover end portion 30 at intervals of approximately60 degrees in angle in the circumferential direction of the cover endportion 30. The fuel pump 1 further includes connection portions 74. Oneof the connection portions 74 is located between the terminal supportportion 71 and the terminal support portion 72 to connect the terminalsupport portions 71 and 72. Another of the connection portions 74 islocated between the terminal support portion 72 and the terminal supportportion 73 to connect the terminal support portions 72 and 73. Theconnection portions 74 are made of resin to be integrated with theterminal support portions 71, 72, 73 and the cover end portion 30. Asshown in FIG. 3, the terminal support portions 71, 72, 73 and theconnection portions 74 have a circular arc shape as a whole when viewedin the center axis Ax1 of the end cover portion 30. In other words, theterminal support portions 71, 72, 73 and the connection portions 74 areshaped like a part of a hollow cylinder cut off.

In the present embodiment, the fuel pump 1 further includes a stopper 81(first stopper) that is made of resin to be integrated with the coverend portion 30. The stopper 81 protrudes from the end surface 35 incontact with an outer wall of the discharge portion 36 as shown in FIGS.1 and 2. In the present embodiment, the fuel pump 1 further includes twosubsidiary stoppers 82 (second stoppers) located on an opposite side ofthe discharge portion 36 from the stopper 81 as shown in FIGS. 1 and 2.The subsidiary stoppers 82 are made of resin to be integrated to thecover end portion 30. The subsidiary stoppers 82 protrude from the endsurface 35 in contact with the outer wall of the discharge portion 36,similar to the stopper 81. The stopper 81 has an upper surface 83 (firstsurface) on an opposite side of the stopper 81 from the end surface 35,and each of the subsidiary stoppers 82 has an upper surface 84 (secondsurface) on an opposite side of the subsidiary stopper 82 from the endsurface 35. The upper surface 83 of the stopper 81 is coplanar with theupper surfaces 84 of the subsidiary stoppers 82. Moreover, the terminalsupport portions 71, 72 and 73 have an upper surface 75 (third surface)on their sides opposite from the end surface 35. The upper surface 75 iscoplanar with the upper surface 83 of the stopper 81 and the uppersurfaces 84 of the subsidiary stoppers 82. When the supply pipe 2 isconnected to the discharge portion 36, the discharge portion 36 isinserted into the supply pipe 2 until an end part of the supply pipe 2contacts the upper surface 83 of the stopper 81 and the upper surfaces84 of the subsidiary stoppers 82. Because the stopper 81 and thesubsidiary stoppers 82 are in contact with the end part of the supplypipe 2, a motion of the supply pipe 2 toward the cover end portion 30 isrestricted.

As shown in FIG. 3, the stopper 81 is arranged at a position adjacent tothe outer rim of the end surface 35 of the cover end portion 30. Theposition of the stopper 81 is distant from the terminal support portion71 and the terminal support portion 73 in the circumferential directionof the end cover portion 30 by approximately 120 degrees in angle. Inother words, the terminal support portion 71, the stopper 81 and theterminal support portion 73 are arranged in an area adjacent to theouter rim of the cover end portion 30 at intervals of approximately 120degrees in angle in the circumferential direction of the cover endportion 30. When a circular area of the end surface 35 is separated intotwo semicircular areas by an imaginary line L1 that is perpendicular tothe center axis Ax1 of the cover end portion 30, as shown in FIG. 3, thestopper 81 can be located within one of the two semicircular area, andthe terminal support portions 71, 72 and 73 can be located within theother one of the two semicircular area. Additionally, the stopper 81 andthe terminal support portions 71, 72 and 73 are arranged on an imaginarycircle C1 in the end surface 35 of the cover end portion 30 as shown inFIG. 3. The imaginary circle C1 has its center at a point located on thecenter axis Ax1.

In the present embodiment, the respective terminal support portions 71,72 and 73 have outer walls 76 coincident with parts of a surface S1 ofan imaginary cylinder as shown in FIG. 3. The imaginary cylinder isdrawn by using the center axis Ax1 as its center axis. The stopper 81also has an outer wall 85 coincident with a part of the surface S1 ofthe imaginary cylinder. The fuel pump 1 of the present embodimentfurther includes convex portions 38 located on outer sides of theterminal support portion 71, the terminal support portion 73 and thestopper 81 in a radial direction of the end surface 35. The convexportions 38 are made of resin to be integrated with the cover endportion 30, and protrude from the end surface 35. Specifically, thenumber of the convex portions 38 is three, and the three convex portions38 are adjacent to the terminal support portion 71, the terminal supportportion 73 and the stopper 81 respectively. Upper surfaces 39 of thethree convex portions 38 located on their sides opposite from the endsurface 35 are coplanar with each other.

As shown in FIG. 2, the relief valve 90 includes a cylindrical portion91, a valve seat 92, a valve member 93, an urging member 94 and a stopmember 95. The cylindrical portion 91 is made of resin to be integratedto the cover end portion 30, and protrudes from the end surface 35 ofthe cover end portion 30. The cylindrical portion 91 is provided apredetermined distance away from the center axis Ax1 of the cover endportion 30. The valve seat 92 is located inside the cylindrical portion91. The valve member 93 has a ball shape, for example, and is capable ofcontacting the valve seat 92. The urging member 94 is a coil spring, forexample, and its one end is in contact with the valve member 93. Thestop member 95 is provided inside an end part 96 of the cylindricalportion 91 located on an opposite side of the cylindrical portion 91from the end surface 35. The stop member 95 is engaged with the otherend of the urging member 94 to fix the other end of the urging member 94in a state where the urging member 94 is compressed in its axialdirection. Thus, the urging member 94 continuously urges the valvemember 93 toward the valve seat 92. In the present embodiment, therelief valve 90 is provided a predetermined distance away from thecenter axis Ax1 of the cover end portion 30. The end surface 35 islocated on the opposite side of the cover end portion 30 from the pumpcover 20, and the valve seat 92 is located on an opposite side of theend surface 35 from the pump cover 20.

The relief valve 90 is capable of reducing a fuel pressure in the space11 between the pump cover 20 and the cover end portion 30 inside thehousing 10, when the fuel pressure in the space 11 becomes higher thanor equal to a predetermined value. When the relief valve 90 reduces thefuel pressure in the space 11, the valve member 93 is separated from thevalve seat 92. Accordingly, it can be avoided that the fuel pump 1 orthe supply pipe 2 is damaged due to an excessive increase in fuelpressure in the space 11.

A processing of the cover end portion 30 performed in a manufacturingprocess of the fuel pump 1 according to the present embodiment will bedescribed with reference to FIG. 4.

(Holding Process)

Firstly, the cover end portion 30 integrated with the terminal supportportion 71, the terminal support portion 73 and the stopper 81 is heldby using three claw portions 101 of a chuck 100. When the chuck 100holds the cover end portion 30, end surfaces of the three claw portions101 tightly contact the outer wall 76 of the terminal support portion71, the outer wall 76 of the terminal support portion 73 and the outerwall 85 of the stopper 81 from outside in the radial direction of thecover end portion 30, respectively.

(Rotation Process)

The chuck 100 rotates the claw portions 101 in a state where theterminal support portion 71, the terminal support portion 73 and thestopper 81 are held via the claw portions 101. Accordingly, the coverend portion 30 is rotated, and an axis of the rotation is coincidentwith the center axis Ax1 of the cover end portion 30. In the presentembodiment, when the cover end portion 30 is rotated, the cover endportion 30 is continuously pressed toward the claw portions 101 in itsaxial direction by using a non-shown jig. Hence, the upper surfaces 39of the three convex portions 38 contacts the three claw portions 101,respectively. In this case, when the claw portions 101 rotate relativelyto the cover end portion 30, and when the claw portions 101 aredisplaced from the upper surfaces 39 of the convex portions 38, the clawportions 101 clash the end surface 35 due to the applied force via thejig. Therefore, it can be detected that there is a failure in theholding of the cover end portion 30 via the claw portions 101, in otherwords, it can be detected that holding positions of the claw portions101 are displaced.

(Cutting Process)

In a cutting process, the press-fit part 31 is cut by using, forexample, a cutting tool 102 in a state where the cover end portion 30 isheld by the chuck 100 and is rotated. Additionally, an inner wall of theshaft cylindrical part 33 that is an example of the bearing portion isalso cut in the cutting process. In the present embodiment, the terminalsupport portion 71, the terminal support portion 73 and the stopper 81are held by the chuck 100, and the press-fit part 31 and the inner wallof the shaft cylindrical part 33 are cut without stopping the holding bythe chuck 100 on the way of the cutting process. Therefore, thepress-fit part 31 and the inner wall of the shaft cylindrical part 33can be processed with a high degree of accuracy so as to be coaxial witheach other.

In the present embodiment, the valve seat 92 of the relief valve 90 isformed after the above-described cutting process. For example, the valveseat 92 can be formed by pressing a shaping jig against a step surfaceinside the cylindrical portion 91 in a state where the shaping jig isheated to have a predetermined temperature or more. The shaping jig hasa ball-shaped end part same as the valve member 93 in shape.Accordingly, the valve seat 92 having a curved surface capable ofcontacting the valve member 93 tightly can be formed. In the presentembodiment, the valve member 93 and the urging member 94, for example,are inserted into an inside of the cylindrical portion 91 after theforming of the valve seat 92. Subsequently, the stop member 95 is madeto contact the end of the urging member 94 opposite from the valvemember 93, and the stop member 95 is pressed into the end part 96 of thecylindrical portion 91 such that the urging member 94 is compressed.Additionally, the end part 96 is melted by heat and is deformed bypressing. When the end part 96 is then cooled to be hard, the stopmember 95 is fixed to the end part 96 of the cylindrical portion 91.

As described above, in the present embodiment, the cover end portion 30is formed into the circular plate shape, and includes the press-fit part31 in the outer rim of the cover end portion 30. The press-fit part 31is press-fitted to the inside of the housing 10, and the cover endportion 30 is located on the other end of the housing 10 in its axialdirection to close the opening of the housing 10. The shaft cylindricalpart 33 that is an example of the bearing portion is provided on thecenter axis Ax1 of the cover end portion 30 to support the other endside of the shaft 52. The relief valve 90 includes the cylindricalportion 91 integrated with the cover end portion 30 to protrude from theend surface 35 on the opposite side of the cover end portion 30 from thepump cover 20, the valve seat 92 formed inside the cylindrical portion91, the valve member 93 contactable with the valve seat 92, and theurging member 94 urging the valve member 93 toward the valve seat 92.The relief valve 90 is capable of reducing the fuel pressure in thespace 11 positioned between the pump cover 20 and the cover end portion30 inside the housing 10 when the fuel pressure becomes higher than orequal to a predetermined value. When the relief valve 90 reduces thefuel pressure, the valve member 93 is separated from the valve seat 92.

In the present embodiment, the end surface 35 is located on the oppositeside of the cover end potion 30 from the pump cover 20, and the valveseat 92 is located on the opposite side of the end surface 35 from thepump cover 20. In other words, the valve seat 92 is located on theopposite side of the cover end portion 30 from the shaft cylindricalpart 33, and is located outside the cover end portion 30. Accordingly,when the valve seat 92 is formed, for example, by heat forming orcutting in the manufacturing process of the fuel pump 1, deformation ofthe press-fit part 31 or the inner wall of the shaft cylindrical part 33due to the forming of the valve seat 92 can be restricted. Therefore,when the fuel pump 1 is used, rotation of the shaft 52 and the impeller55 is stabilized, and a fuel discharge capacity can be therebystabilized. Furthermore, the end surface 35 is located on the oppositeside of the cover end potion 30 from the pump cover 20, and the valveseat 92 is located on the opposite side of the end surface 35 from thepump cover 20. Therefore, as an additional effect, a metallic die forforming the cover end portion 30 of the present embodiment can be usedas a metallic die for forming another cover end portion that does notinclude a relief valve (valve seat).

In the present embodiment, the relief valve 90 is provided apredetermined distance away from the center axis Ax1 of the cover endportion 30. In other words, the valve seat 92 is provided apredetermined distance away from the shaft cylindrical part 33 locatedon the center axis Ax1 of the cover end portion 30. Therefore, when thevalve seat 92 is formed by, for example, heat forming or cutting in themanufacturing process of the fuel pump 1, the deformation of the innerwall of the shaft cylindrical part 33 due to the forming of the valveseat 92 can be restricted certainly.

Furthermore, in the present embodiment, the relief valve 90 includes thestop member 95 provided inside the end part 96 of the cylindricalportion 91 to fix the end part of the urging member 94 that is locatedon its side opposite from the valve member 93. The end part 96 of thecylindrical portion 91 is melted by heat and is deformed by pressing,and the end part 96 is then cooled to be hard such that the stop member95 is fixed to the cylindrical portion 91. The relief valve 90 isprovided a predetermined distance away from the center axis Ax1 of thecover end portion 30. Therefore, in the manufacturing process of thefuel pump 1, deformation of the inner wall of the shaft cylindrical part33 due to heat and pressure utilized in the fixation of the stop member95 to the end part 96 of the cylindrical portion 91 can be restricted.

Although the present disclosure has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications described below will become apparent to those skilled inthe art. The relief valve 90 may be provided to be adjacent to thecenter axis Ax1 of the cover end portion 30. The valve seat 92 of therelief valve 90 may be formed by cutting. The terminal support portions71 to 73, the stopper 81 and the subsidiary stopper 82 may be omitted.The convex portions 38 also may be omitted.

The bearing member 34 fitted into the inner side of the shaftcylindrical part 33 and the bearing member 62 fitted into the holeportion 61 of the pump casing 60 may be omitted, and the shaft 52 may besupported directly by the inner wall of the shaft cylindrical part 33 ofthe cover end portion 30 and by the inner wall of the hole portion 61 ofthe pump casing 60. The cover end portion 30 may be separated from thestator 40.

The material of the whole rotor 50 is not limited to the bond magnet.For example, the rotor 50 may be obtained by attaching a magnet, such asa bond magnet or a sintered ferrite magnet, to an outer wall of acylindrical rotor core. The motor part including the stator 40, therotor 50 and the shaft 52 has an inner rotor structure in which a rotoris located inside a stator. When the motor part has the inner rotorstructure, the motor part is not limited to the above-describedthree-phase motor. Therefore, the motor part may be driven by usingmultiple phases other than three phases. Furthermore, the motor part maybe structured as a brushed motor.

The fuel-supplied object is not limited to the internal combustionengine, and the fuel-supplied object may be thereby another device thatrequires supply of fuel. The fuel pump of the present disclosure is notlimited to use for fuel, and thus may introduce therein and dischargeother fluid such as liquid or gas. The present disclosure is not limitedto the above-described embodiment, and is feasible in variousembodiments without departing from the scope of the present disclosure.Additional advantages and modifications will readily occur to thoseskilled in the art. The disclosure in its broader terms is therefore notlimited to the specific details, representative apparatus, andillustrative examples shown and described.

What is claimed is:
 1. A fuel pump comprising: a housing having a hollowcylindrical shape; a pump cover closing an end opening of the housing ona first side of the housing in an axial direction of the housing, thepump cover including a suction portion; a cover end portion having acircular plate shape to close the other end opening of the housing on asecond side of the housing in the axial direction of the housing, thecover end portion including a press-fit part that is located on an outerrim of the cover end portion to be press-fitted to an inner side of thehousing; a stator having a hollow cylindrical shape, the stator beingaccommodated inside the housing and including a plurality of woundwires; a rotor rotatably provided inside the stator; a shaft providedcoaxially with the rotor to rotate together with the rotor; an impellerconnected to one end of the shaft, wherein the impeller rotates togetherwith the shaft to draw a fuel through the suction portion and pressurizethe drawn fuel; a bearing portion provided in the cover end portion on acenter axis of the cover end portion to slidably support the other endof the shaft; a discharge portion provided in the cover end portion tobe used as a port through which the fuel pressurized by the impeller isdischarged; and a relief valve capable of reducing a fuel pressure in aspace provided between the pump cover and the cover end portion in thehousing when the fuel pressure in the space becomes higher than or equalto a predetermined value, wherein the relief valve includes: acylindrical portion integrated with the cover end portion to protrudeoutward from an end surface of the cover end portion on the second sideof the housing; a valve seat provided inside the cylindrical portion; avalve member capable of contacting the valve seat; and an urging memberhaving an end part contacting the valve member to urge the valve membertoward the valve seat, the valve member is separated from the valve seatwhen the relief valve reduces the fuel pressure in the space, and thevalve seat is located outside the cover end portion on the second sideof the housing.
 2. The fuel pump according to claim 1, wherein therelief valve is located a predetermined distance away from the centeraxis of the cover end portion.
 3. The fuel pump according to claim 2,wherein the relief valve further includes a stop member that is providedinside an end part of the cylindrical portion to fix another end part ofthe urging member on an opposite side of the urging member from thevalve member, and the end part of the cylindrical portion extendsradially inward of the cylindrical portion to fix the stop member insidethe cylindrical portion.
 4. The fuel pump according to claim 3, whereinthe end part of the cylindrical portion is deformed by thermal melting,pressing and subsequent cooling to extend radially inward of thecylindrical portion.